Mixtures of polyisoprene rubber and polypentenamer

ABSTRACT

RUBBER MIXTURES CONTAINING (A) 5-95% BY WEIGHT OF POLYISOPRENE RUBBER AND (B) 95-5% BY WEIGHT OF TRANS-1,5-POLYPENTENAMER.

United States Patent 3,769,369 MIXTURES 0F POLYISOPRENE RUBBER AND POLYPENTENAMER Wilhelm Graulich, Opladen, Manfred Beck, Odenthal- Globusch, Gunter Marwede, Leverkusen, and Dieter Theisen, Remscheid, Germany, assigmors to Bayer Aktiengesellschaft, Leverkusen, Germany No Drawing. Filed May 10, 1972, Ser. No. 252,027 Claims priority, application Germany, May 12, 1971, P 21 23 452.6 Int. Cl. C08d 9/08 US. Cl. 260-887 6 Claims ABSTRACT OF THE DISCLOSURE Rubber mixtures containing (a) -95% by weight of polyisoprene rubber and (b) 95-5% by weight of trans-1,5-polypentenamer.

This invention relates to mixtures of 5 to 95% by weight of polyisoprene rubber and 95 to 5% of polypentenamer.

Preferred mixtures consist of 50 to 95% by weight of polyisoprene and 50 to 5% by weight of polypentenamer.

Polyisoprene rubberswithin the meaning of this invention are polymers of isoprene (Z-methyI-butadiene- (1,3)) which have rubber-like properties.

Especially suitable are those polyisoprenes in which more than 70% of the double bonds and, in particular more than 85% are in the cis-configuration and in which the linkages are predominantly 1,4-linkages, e.g. at least 80% of the monomer units are linked in this Way.

Polyisoprenes of this kind are known compounds and are already produced on a large scale. They have been generally described, for example, in Polymer Chemistry of Synthetic Elastomers, Part H, edited by J. P. Kennedy and E. Tornquist Interscience Publishers, New York, 1969, pages 633 and 643 or in Polyisoprene Elastomers by D. Oosterhof, which appeared in Chemical Economics Handbook of the Stanford Research Institute, Menlo Park, Calif., 1969 or P. Schneider Stereo-Polyisoprene, Ullmanns Ecyklopadie der technischen Chemie, 3rd Edition, pages 369-372, publishers Urban and Schwarzenberg, Munich, 1970.

Cis-1,4-polyisoprenes are very similar to natural rubber and have certain advantages, e.g. high elasticity and high abrasion resistance so that they are used in making automobile tires and technical rubber articles.

Compared with natural rubber, cis-l,4-polyisoprenes have a lower green strength and building tack. Both natural rubber and polyisoprenes have not much stability to reversion and to ageing on account of their chemical constitution. They can only be extended with small quantitles of plasticiser oils.

Cis-l,4-polyisoprenes used in this invention can be made by art recognised methods, e.g. by polymerising isoprene with Li-alkyl or with organometallic catalysts of the Ziegler-Natta type, e.g. according to Belgian Pat. No. 726,447.

It is an object of this invention to improve the physical properties of cis-1,4-polyisoprene, i.e. its green strength, building tack, oil-extendability and stability to ageing and degradation. It was found that these properties are decisively improved by mixing polyisoprene and trans-1,5- polypentenamer.

ice

Trans-1,5-polypentenamer is prepared, i.a. by ring opening polymerisation of cyclopentene with organometallic catalysts according to art recognised processes, e.g. according to German Pat. No. 1,299,868. The product is well known in the art. For this invention polypentenamers with rubber-like properties having at least 30% of their double bonds in trans-configuration are preferred. The trans double-bonds can form blocks or may be statistically distributed.

Mixtures of cis-l,4-polyisoprene and trans-1,5-polypentenamer are prepared either from the solid rubbers on conventional rubber processing machines or by blending rubber solutions in organic solvents and isolating the rubbers by removing the solvent. The mixtures have a much higher green strength and building tack than was expected from the arithmetic mean of the individual rubbers.

The degradation and ageing stability of cis-l,4-polyisoprene is also improved to a greater extent by the addition of trans-1,5-polyisoprene than is commensurate with the proportion of trans1,5-polyisoprene added. Furthermore, the mixtures can be extended With a larger amount of extender oils than is normally tolerated by cis-1,4-polyisoprene without deleterious effect.

The mixtures according to the invention of cis-1,4-polyisoprene and trans-1,5-polypentenamer contain 5 to by weight of polyisoprene and 95 to 5% by weight of polypentenamer. Mixtures of 50 to 95% by weight of polyisoprene and 5 to 50% by weight of polypentenamer are preferred.

These mixtures have excellent building tack and green strength. They are homogeneous and they can readily be covulcanised. Thus they are most suitabl rubbers for producing automobile tires and other technical articles of manufacture.

In the following examples, parts are parts by weight and percent are percent by weight unless otherwise indicated.

EXAMPLE 1 Mixtures having the formulations indicated below were prepared on a roller mill, from a polyisoprene having 'a Mooney viscosity of 90 and containing more than 98% of cis-l,4-bonds and a polypentenamer containing 86% of trans-double bonds and having a Mooney viscosity ML-4 (100 C.) of approximately Total 100 parts.

Strips measuring 6.2 mm. in width, 50 mm. in length and 1.5 mm. thickness are prepared from the mixtures and placed on a fabric which has been treated to give it a good affinity with rubber, and the strips are then covered with an aluminium foil and pressed for 3 minutes at 110 C. A completely smooth surface is obtained.

After removal of the foil, two such strips are pressed together over a contact surface of 38.44 mm. and kept under a pressure of 2.25 'kg./cm. (=loaded with a weight of 16 ounces) for 10 seconds. A pull is then exerted on the contact area to pull the strips apart at the rate of 0.46 mmjsec. The force in grams counteracting the pull is known as the bond strength.

The green strength is expressed as the tensile strength of the crude mixture in kg./cm. according to DIN 53504.

TABLE I Cis-l, 4-polyisoprene 100 90 80 70 60 50 Trans-1,5-plypentenamer 100 30 40 60 Bond strength (g):

Formulation 1-. 850 2, 260 1, 310 1,680 1, 810 2, 020 2, 010 Formulation II 670 2, 040 990 1, 200 1, 400 1, 510 620 Green strength (kg./

Formulation I 8 28 13. 2 16. 8 18. 9 20. 2 22. 0 Formulation II 6 22 10. 1 13. 2 14. 0 15. 1 16. 3

The ageing stability was tested on Vulcanisates prepared from the following formulation:

- Total 100 parts.

The rubber mixtures were vulcanised in a press by heating 150 for 30 minutes.

The ageing stability was tested by treating vulcanisate samples with hot air at 100 C. in an oven according to DIN 53 508. The test samples were standard test rods according to DIN 53 504. The properties determined before and after hot air treatment for the specified forms were the tensile strength, elongation at break and modulus at 300% elongation according to DIN 53 504 Cis-1,4-polyisoprene 100 90 80 70 60 50 Trans-1,6-poly'pentenamer 100 10 20 30 40 50 B efore ageing:

Tensile strength (kg/c1113) 208 205 207 206 210 201 208 Elongation (percent) 460 490 470 510 505 490 510 Modulus 300% (kgJcm-L- 97 103 101 104 102 105 104 Ageing for 7 days at 100 0.

hot air:

Tensile strength (kg/0111.) 138 210 170 185 193 200 201. Elongation (percent) 250 515 420 435 450 505 490 Modulus 300% )kgJcmfi) 115 135 135 129 112 114 Ageing for 14 days, 100 0.

hot air:

Tensile strength (kg/cm!) 59 212 101 122 138 152 164 Elongation( ercent) 210 465 330 390 425 460 480 Modulus 30 o (kg./cm.)-- 00 137 148 143 139 135 119 Ageing for 21 days, 100 0.

hot air:

Tensile strength (kg/cm!) 208 89 102 124 156 162 Elongation( ercent 425 270 325 370 405 450 Modulus 300 0 (kg/0111. 145 132 127 133 123 The ozone stability was tested on Vulcanisates of the following rubber mixtures:

a Total 100 parts.

The ozone stability of these mixtures was tested by a method of Farbenfabriken Bayer AG which is similar to DIN 53 509:

The stability to 5'0 p.p.h.m. of ozone at a temperature of 40il C. for up to 7 days was determined. It was assessed by recording the number of hours before cracking begins at various degrees of elongation.

Cis-1,4polyisoprene-- 100 80 70 60 50 Trans-1,5-polypentenamer 10 20 30 40 50 Beginning of cracking At elongation of 10% 168 168 168 168 168 168 168 At e ongation of 0 48 168 80 144 150 168 At elongation of 30 24 168 55 80 120 144 168 At elongation of We claim:

1. A rubber mixture comprising (a) 5 to 95% by weight of polyisoprene rubber and (b) 95 to 5% by weight of trans-1,5-polypentenamer rubber.

2. A mixture as claimed in claim 1, which comprises (a) 50 to 95 of polyisoprene rubber and (b) 50 to 5% of trans-1,5-polypentenamer rubber.

3. A mixture as claimed in claim 1 in which the polyisoprene is a cis-1,4-polyis0prene.

4. A mixture as claimed in claim 3 in which the cis- 1,4-polyisoprene has more than 70% of the double bonds in the cis-configuration.

5. A mixture as claimed in claim 1 in which the trans- 1,5-polypentenamer has more than 30% of the double bonds in the trans-configuration.

6. Vulcanisates produced by vulcanising a mixture as claimed in claim 1.

References Cited UNITED STATES PATENTS 3,337,520 8/1967 Bjornson et al 260--94.3

FOREIGN PATENTS 1,062,367 3/1967 Great Britain 260887 MURRAY TILLMAN, Primary Examiner J. ZIEGLER, Assistant Examiner US. Cl. X.R.

260--28.5 A, 33.6 AO 

